Telephone system



Oct. 20, 1936.: E. WOCHINGER TELEPHONE SYSTEM Filed July 11, 1935 2 Sheets-She 2 omwmm omwmwfi 2 N 8% 5 Hmmo; mssmm o8 NE; 5 Iv QmaSM 3%.

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EDUARD WOCHINGER ATTORNEY.

Patented Oct. 20, 1936 rrso STATES TELEPHONE SYSTEM Eduard Wochinger, Berlin, Germany, assignor to Siemens & Halske Aktiengesellschaft, Siemensstadt, near Berlin, Germany Application July 11, 1935, Serial No. 30,925 In Germany July 12, 1934 6 Claims.

The present invention relates to telephone systems with main and subsidiary exchanges and automatic operation, especially to systems in which selectors in the subsidiary exchange are set on both calling and called subscribers lines and. also into normal position by switching devices in the main exchange.

For fuller utilization. of the connecting lines and devices and for quicker establishment of IO calls it is advantageous for the selectors of the subsidiary exchange and the switching devices of the main exchange in such systems, to be in such a condition during the release motion at the end of a call that calls occurring during this release motion can immediately be taken up. This, of course, must be prevented, however, in the case of the selectors and switching devices becoming out of step, when wrong connections and similar derangement of the working may occur. This is achieved by the invention in that switching means are provided which, when the selectors of the subsidiary exchange and (or) the switching device of the main exchange which control them have become out of step, prevent the establishment of an outgoing call over the selectors of the subsidiary exchange during the release motion of the selectors and switching devices which have become out of step.

Fig. 1 shows my invention applied to a system in which a subsidiary exchange is connected to a main exchange.

Fig. 2 shows my invention applied to a system in which calls may be established between subscribers in the subsidiary exchange as well as between a subscriber in the subsidiary exchange and a subscriber in the main exchange.

In Fig. 1 a subsidiary exchange UA without batteries is shown as an embodiment of the invention, which has access to a main exchange I-IA over the connecting line consisting of two leads.

The connection of the subsidiary exchange subscribers to this connecting line takes place over a selector DBII! which for outgoing calls acts as a call finder, and for incoming calls is set by numerical impulses as a final selector. In the normal condition of the system relay LID, and further relays (LII, LIZ) in case the contacts to be provided for each subscriber cannot be operated by one relay, is operated over one lead of the connecting line. These relays connect all the subscribers of the subsidiary exchange in common to the calling circuit through their working contacts and on deenergizing which occurs when a subscriber calls, cause a switching over of the 5 calling circuit so that the individual subscribers can be tested. In order to reduce the number of relays of this kind to a minimum, contacts operated mechanically by the selector of the subsidiary exchange are used for this purpose, for example IwIIl (I-I'I) and which are opened on 5 the first switching motion of selector DBI!) and remain open until position H.

The setting of selector DBIII in the subsidiary exchange UA always takes place under the control of the main exchange HA, both in case of 10 outgoing calls, when the selector is acting as a call finder, and also in the case of incoming calls when the selector is acting as a final selector.

As already mentioned, in the normal position of the system, relay LIIl, and, if present, also re- 5 lays LII and L!2 are energized, over the circuit: earth, relays LIZ, LII, LII), wiper a in position 0, winding I of relay UIIl, lead a. of the connecting line, contacts Z'Iclll, 39anIEI, wiper dIvII) in position 0, contact 431cm, winding I of relay XI 0, bat- 20 tery, earth. In this circuit only relays LIII, LII and LIZ are energized, while relay XII) does not receive sufiicient current.

Outgoing trafiic 95 When subscriber AI of the subsidiary exchange takes up his receiver the following circuit is set up: earth, contact 22mm, winding II of relay UI B, wiper b in position 0, lead bl, subscriber AI, lead aI, contact IwIIl (Il1), wiper a in position 0, 3 Winding I of relay UII], lead a, contacts 210), 39anl0, wiper dIVIIl in position 0, contact 43:1:I0, winding I of relay XII], battery, earth. Besides the transitory energizing of relay KN relay XIII also energizes in this circuit and locks up by 35 the closing of contact 42M!) in series with its winding II. The circuit just described passing over the a lead is opened at contact 43mm. In the subsidiary exchange relays LID, LII, and LIZ release so that the switching magnet WIIl of the 4,0 selector in the subsidiary station is connected to the b lead over contact 23ZIO. The following circuit is thus set up through the main exchange: earth, contact 231 I 0, switching magnet WIO, contact 22am, lead b contacts 24cm, 48g), 45 relay KID, battery, earth. In this circuit both the switching magnet in the subsidiary exchange and also relay KIO in the main exchange are energized so that the switching device in the subsidiary exchange is advanced one step. Con- 50 tact 52kIIl switches on the switching magnet Dlll in the main exchange through contact 53h), so that the Wipers D I I0 -d IV I0 operated by this switching magnet also advance one step. Through contact 51d), which is operated each 55 time switching magnet DIII energizes, relay YIII is energized over: earth, contact E'IdIIl, resistance Wi l, winding I of relay YIO, battery, earth. Thereupon the energizing circuit of switching magnet WIII and relay KIIJ, completed over the b-lead of the connecting line, is broken at contact 48y). Switching magnet DI is likewise disconnected by the opening of contact 5210). The interaction would, if necessary, be repeated again and accordingly both the switching device.

DBIII in the subsidiary exchange and also the switching device in the main exchange would be advanced in step. Since, however, the subscriber AI of the subsidiary exchange, connected to the first contact is calling, the testing relay PIII, which after the occurrence of each step is connected to the a-lead over contact 45yIIi, is energized in the main exchange after the first step. This testing circuit is completed through: earth, contact ZIIuIIl, winding II of relay UIII, wiper b in position I, lead bI, subscriber AI, lead aI, wiper a. in position I, winding I of relay UIO, lead a, of the connecting line, contacts 210), 391111"), wiper dIVIIl in positions I-I I, contacts 44mm, 45y), relay PIIi, battery, earth. In the same circuit relay UII': is energzied in the subsidiary exchange. By the closing of contact 5811), relay YI is next maintained energized over its winding I, while by the opening of contact 2Zul0 the switching magnet Will of the switching device in the subsidiary exchange is cut off. The earth previously connected over contact MM 6 is replaced by earth connected over contacts 24cm, M' III, 46km and choke coil DrII, by the opening of contact ZIluIB and the closing of contact ZIuIIl, so that complete symmetry exists between the two speaking leads, and no unbalance occurs in the subsidiary exchange. By the closing of contacts 3IpI a loop is also closed for seizing the exchange connecting devices, so that for example a preselector can be set in operation after whose setting relay C01 is energized. The subscriber receives a dialling signal. He can then commence dialling.

On operating the dial the relay PII! in the main exchange used for testing while the selector is being set releases intermittently according to the impulses, while relay UIIJ in the subsidiary exchange remains energized on account of its construction as a slow acting relay. Relay YIII similarly holds up in the main exchange during the impulse emission. Contact 3IpIII transmits the impulses to the connecting devices of the main exchange by interrupting the line loop. On the first release of relay PIIJ relay VI is influenced since contact IzrIIl is also closed. The latter relay ensures a clean transmission of the impulses by short circuiting the choke coil DTIO at contact 3012i!) during the emission of the impulses, and disconnecting the condensers (contacts 28v! and 29m).

The connecting devices of the main exchange are set in the desired direction by the various impulse trains in any suitable manner, with which we are not concerned, and the desired subscriber is then rung in the known way.

It should be noted that the meters of the subsidiary exchange subscribers are centralized in the main exchange. In order now to be able to influence the corresponding meter when a subscriber sets up a call the meter is connected over a wiper of the switching device in the main exchange which controls the setting of the selector in the subsidiary exchange and is thus advanced in step with the latter. When the conversation has finished a meter impulse is transmitted over the lead 0, in any way, with which we are not concerned, which influences the meter SMI allocated to the calling subscriber. A second winding of relay YI lies in the meter circuit and on energizing maintains the connection existing between the main exchange and the subsidiary exchange so that even when the calling subscriber replaces his receiver no release of the selector DBI I] in the subsidiary exchange or of the switching device in the main exchange can take place during the metering process. If at the moment that the selector of the subsidiary exchange is engaging a subscribers line during the further switching after the termination of the conversation the subscriber of the line in question takes up his receiver, the connecting line leading to the main exchange can immediately be seized again. Since the selector of the subsidiary exchange has advanced in step with the switching device in the exchange, in this case also the meter corresponding to the subscriber reached is again connected to the c-lead.

If a new call does not take place, both switching devices are advanced to position I! through the alternating play of the above mentioned relay. In the main exchange relay l-IIIB energizes in this switching position over contact 38yI I], wiper (2 III III and resistance Wi'I, and by opening contact 53MB prevents the switching magnet DI from being operated again and the consequent further switching of the corresponding wiper. The switching magnet W I E in the subsidiary exchange is further operated, however, by the alternate play between relays KI 0 and Y I 5, since the corresponding selector has to carry out 1'7 steps to reach the zero position. This is continued until the selector DBI I] in the subsidiary exchange reaches position II. In this position relays LID, and LII and LIZ now energize over: earth, relays LIZ, LII, LII), wiper a in position I'I, winding I of relay UI 9, lead a of the connecting line, contacts 2'IcIE, 390mm, IIIhII), resistance WiE, battery, earth. Relay LIQ cuts off the operating circuit of switching magnet WII), at contacts 23MB, so that relays KII) and YIII in the main exchange can also no longer energize. By the opening of contact 38MB relay HII! deenergizes and opens the circuit for the L-relay passing over the a:-lead, at contact liihill. Thereupon this relay again deenergizes. Through the closing of contact 23ml the operating circuit of switching magnet WIIl passing over the b-lead oi the connecting line is again closed so that the selector in the subsidiary station makes one switching step (into the normal position). By relay KIIE energizing in the operating circuit of switching magnet WIB the switching magnet of the switching device in themain exchange is now operated over contact 52k I D, so that this switching device also makes. one step, likewise into the normal position. Thus both are now standing again in position I]. On reaching this position the condition existing when the system is at rest is again set up (L-relay energized).

The number of steps of the selector in the sub sidiary exchange are known to be larger than the number of steps of the switching device in the main exchange. Since, however, in order actually to connect up the meter of the calling subscriber through the switching device in the main exchange, the switching device and the selector in the subsidiary exchange must be synchronous, the arrangement is such, as described above, that the motion is synchronous until the I Ith contact, i. e. until the first contact without any subscribers tact 3'hmlli.

leasemotion is achieved in that up until the llth contact the relays KID, YIl and'the magnet DID produce impulses for advancing both switching devices, whereupon the magnet DH] is discon-- nected from the impulse producing. circuit and by a switching over process (I-IIIJ) impulses are only produced through relays KI!) and Ylll for the magnetWlU. In position H this then causes a reversal of the change-overdevice so that for the last switching step the circuit first operative comes into operation again, together with the switching magnet D I ll.

Incoming tra fic The'subscribers attached to the subsidiary station can obviously also be called from the main station. The last digit of their call numbers corresponda for example, to the number of steps which the selector DBlll in' the subsidiary exchange must be taken in order to be set on their connections. If they were previously subscribers having individual lines to the main exchange they can retain their original call numbers unaltered. Only the c-lead from the final selector has to be disconnected from their previous connections and led to a contact of wiper d I). The aand b-leads of all subscribers lines incoming from the final selector are connected together in parallel. Thus both subscribers attached to the same level of a final-selector and also those attached to different levels of the same final selector or in particular to differentfinal selectors are incorporated in the subsidiary exchange while maintaining their call numbers.

If a final selector (not shown) is set in any manner on the line leading to the subsidiary exchange for the purpose of calling subscriber A5, testing is carried out, in the known way, over the lead 05 thus seized, as to whether the line leading to the'apartment house exchange is free. If this is not the case, wiper d III ID has left its position 0, so that the lead 05 incoming from the final selector is open and the calling subscriber receives an engaged signal in the known way.

If on the contrary the line leading to the subsidiary exchange is free relay Anlll is energized over the lead c5 (lead 05, resistance Wi9, contact 36110, relay Anifl, wiper d III H in position 0, resistance Wi'i, battery, earth). Relay Anlfl lies in a circuit dependent upon wiper d III I0, via con- Through the opening of contact 39am il-the circuit existing the relays L10, Li I and M2 in the normal condition of the system is broken, so that these relays deenergize. Seizing from the subsidiary exchange is not possible since relay P58 which is otherwise used for testing is disconnected and theselector is brought to rest through setting the switching device in the main exchange under the control of the seized testing lead. By the closing of contact 231 I 0 after the release of relay L!!! the operating circuit for the switching magnet passing, over the b -lead is closed in series with relay Kl 0. Both switching devices nowmove synchronously as was described above for the case of the call of a subscriber of the subsidiary exchange. The advancement now, however, takes place until the wiper d I ll] comes to rest on the calling lead 05. When this occurs relay 0H) energizes over the circuit: lead 05, wiper d I I0, contact 32 anlll, relay C10, battery, earth.

1' By the opening of contact 240! 0 the operating cirleads are switched through to the final selector by the closing of contacts cl0 and 26040. The ringingcurrent is transmitted .to the desired subscriber from the final selector in any of the known ways, andpasses over the a-lead of the connecting line of the subscribers station in the subsidiary exchange and the earth in the subsidiary station connected over contact 2011,). If the ringing current were connected over the b-line, then obviously the aand b-leads must be interchanged.

When the called subscriber replies the ringingcurrent'is disconnected by the completion of the loop in' the final selector, and by the energizing of relay- UIO over the speaking leads contact.

ZlulU is closed so that now lead b of the connecting line is also switched through to the main exchange. The desired subscriber is now connected'tc the calling subscriber.

After the termination of the conversation lead 05 is cut off from the final selector in any desired Way; so that relays CH] and Anlfl, which had established a locking circuit over contact 350), release. In the subsidiary exchange relay UN) is deenergized so that the operating circuit for magnet WIB in the subsidiary exchange and for relay KID in the main exchange is again completed over the b-lead of the connecting line. By relay Kill, the magnet Dill of the selector'in the main exchange is switched on through contact 5270). Thus the reciprocal play between the two switching devices, already described, causes the advancement into the normal position in the manner described in the case of the release for anoutgoing connection.

Special circuits If the selector in the subsidiary exchange is displaced from position 0 by hand, and the two switching devices thus become out of step, relaysmagnet DIU in the main exchange is switched on by relay KID, so that both switching devices are advanced under the control of the impulse circuit in the main exchange. Since in this case both switching devices are not synchronous the possibility of a subscriber who hangs up during the advancement into the normal position, causing the connecting line leading to the main exchange to be seized must be prevented, for otherwise the' meter of another subscriber would be operated in the main exchange. This is prevented in that through the displacement of the selector in the subsidiary exchange by hand, in contrast to the procedure in a normal call, relay Klil is energized in the main exchange, so that the testing relay Plfl in the main exchange is not connected over contact Marlfl, i. e. this relay cannot test and thus the advancement of the switching device into the normal position cannot be interrupted. For the rest the release motion occurs in the same way as after the normal establishment of a call, i..e. advancement in step until the eleventh contact of the switch in the main exchange is reached, then the selector of the subsidiary exchange is controlled alone until position 11, and then the last step to the zero cuit; of magnet Will and alsothe control circuit: for'the magnet Dill-are broken. The speaking.

(ill) LIO,L!! and L!2 again deenergize, whereupon the magnet Wl0 in the subsidiary exchange is again connected in an operating circuit over contact 23 l 60, and is influenced by the reciprocal play of relays KM) and Yi0, partly together with the switching magnet Dl0 in the main exchange, and partly independently, as mentioned above, until the zero position is reached. They can then operate synchronously again when the next call is set up.

Each seizing of the devices in the main exchange can be .indicated by a seizure lamp L. If desired, each seizing direction can be indicated specifically, if the contacts 550!!! for the outgoing seizing and 55am!!! for the incoming seizing are wired separately.

In Fig. 2 a system with a main and subsidiary exchange is illustrated as an embodiment of the invention. This in addition to the outgoing and incoming calls enables connections to be set up between subscribers of the same subsidiary exchange. For this purpose, in addition to selector DB30 which serves for setting up outgoing and incoming calls (exchange calls) and thus works as a double purpose selector, a second selector LW30 is provided in the subsidiary exchange which serves' to set up interval connections within the subsidiary exchange. This auxiliaryselector is. connected over an auxiliary line (a2 b2) between the subsidiary exchange and main exchange to the connecting line leading to the main exchange which is seized by calling subscribers.

In order to differentiate between the difierent call directions i. e. outgoing exchange calls and internal calls, an additional switching device is provided (magnet D230, wipers dz I 30di IV 30) in the main exchange which is switched round according to the characterizing number dialled so that either a call is set up over the connecting devices of the main exchange, or the auxiliary selector LW30 in the subsidiary exchange can be set on the desired subscribers connection. In the present embodiment the characterizing is arranged so that by dialling the digit I an outgoing exchange call is characterized, while by ialling the subscribers number directly, i. e., any digit except i, an internal call and thereupon the subscriber desired in the internal call, is characterized.

The characterizing digit for the outgoing exchange call is not taken up by the connecting devices'in the main exchange, but only by the characterizing switching device and the auxiliary selector LW3 provided in the subsidiary exchange.

In the normal condition of the system all the selectors both in the subsidiary exchange and also the switching devices in the main exchange and inaddition all the relays, are uninfluenced.

Outgoing calls When a subscriber takes up his receiver and momentarily depresses the key, for example B2 inzxthecase of subscriber A2, earth is connected to lead a! of the connecting line leading to the main exchange. In the main exchange relay X30 energizes over the circuit: earth, battery, resistance W219, wiper d II 30, winding I of relay X30, contacts 345:1:30, 348an30, 350030, lead a!, winding I of relay U3 I, wiper a! of selector DB30 in position 0, key B2, earth. Relay X30 locks up'over its winding II on closing its contact 313x30. Contact 345x30 disconnects battery from the lead a! of the connecting line. Contact 331x30, however, connects battery to the I)! lead. The following circuit is then set up: earth, magnet W3i, contact 309113! B! lead of the connecting line, contacts 335030, 331x30, 339e30:, 3421/30, relay K30, battery, earth. In this circuit the magnet W3! energizes in the subsidiary exchange and relay K30 in the main exchange, so that the selector DB30 in the subsidiary exchange advances one step. Similarly the switching device influenced by the magnet D30 in the main exchange is advanced one step, after this magnet has been energized'over contact 3|6lc30. On the energizing of this magnet contact 3| M30 is closed and thus relay Y30 is switched on over resistance W224. This relay opens its contacts 342y30, among others, so that the operating circuit of magnet W3! and relay K30 is broken, so that these are both deenergized. By the opening of contact 3l67c30 magnet D30 is also deenergized which again results in the opening of contact 3l8d30 and hence the deenergizing of relay Y30. Contact 3 i2y30 is again closed and thereby the operating circuit for magnet W3! and for relay K30 is set up afresh, so that selector DB30 in the subsidiary exchange and the switching device in the main exchange which is influenced by relay K30, advance a further step. I

Since the calling subscriber A2 is connected to the second contact of selector DB30, on reaching this contact after relay Y30 has operated as before after the completion, of the second switching step, the following circuit is set up: earth, battery, relay P30, contacts 3411/30, 346x30, 348G7Z3D, 350030, lead a! of the connecting line, winding I of relay U3 I, wiper a! of selector DB30 in positionZ, subscriber A2, wiper b! of the same selector in position 2, winding II of relay U3l, contacts 301u3l, 306w32 (mechanically operated by LW 30, earth. It should be noticed that the connection of the testing relay P30 to lead a! by relay Y30 takes place after each step of the switching device in the main exchange. By the closing of contact 3|9p30 relay Y30 is held energized so that by the opening of contact '342y30 further transmission of impulses for advancing the switching device is prevented. Earth is connected to lead I)! over contact 340y30 and the choke Dr3!, so that after opening contact 301u3! and closing contact 308143! the following locking circuit is set up for relay U3l, energized in the above testing circuit: earth, choke coil' Dr3l, contacts 34!]c30, 340 30, wiper d IV 30 in position !!l, contact 335030, lead b! of the connecting line, contact 308u3l, winding II of relay U3!, wiper b! of selector Db30 in position 2, subscriber A2, wiper a! of selector DB30 in position 2, winding I of relay U3I, lead 0.! of the connecting line, contacts 350030, 348'an30, 345330, 3411130, relay P30, battery, earth. At contact 3541030 a loop is closed for the connecting devices of the main exchange sothat just as in the case of a subscriber having an individual line, a preselecting device, for example a call finder, is set in operation. After the setting of such a preselecting device, if the calling subscriber is connected to a free connecting device he received a signal from the exchange.

Since it is an outgoing call which is being set up in the present case, the subscriber must dial the characteristic digit 1. It should be added that relay J30 was energized over contacts 324x30 and 3261230 and also over wiper dz III 30 in position 0, so that contact 3541030 which was closed by the testing relay P30 which operates as the impulse relay during the numerical selection, is shunted by contact 355730. The selection of the characterizing digit 1 is accordingly not transmitted to the connecting devices of the main exchange. On the first impulse i. e. on the first deenergizng of relay P30 the magnet Dz'30 of the characterizing switching device is operated in the main exchange over contacts 323x30, 3211030, and 328730, and relay V30 is operated in parallel with the magnet; moreover, by the transitory closing of contact 3151030, battery is connected over contact 314130 to the b2 lead of the auxiliary connecting line and hence magnet W32 of the auxiliary selector LW30 is operated, By means of relay V30, energized during the impulse emission, the choke coil Dr30 is short circuited by the closing of contact 352 .230, and by the opening of contacts 35lv30 and 3531230 the condensers in the speaking leads are disconnected so as to ensure a more clear impulse emission. After the one impulse has been given relay V30 deenergizes on account of the prolonged opening of contact 3271930, so that relay J30, which after one step has been made, can hold up over Wiper diIII 30 in position I and over contact 32551130, is deenergized. The short circuit of impulse contact 354103 is accordingly removed by the opening of contact 3552'30 so that the next impulse trains can be transmitted to the connecting devices of the main exchange. The magnet W32 in the subsidiary exchange, which previously displaced the auxiliary selector LW30 one step, can no longer be efiected since the corresponding circuit is broken at contact 314130.

When the desired subscriber is reached, after testing on the contact in the normal way, ringing current is transmitted and the speaking connection is established on the desired subscriber replying. When the conversation has finished a metering impulse is transmitted on the c-lead in any desired manner which does not concern us here. This is extended to the meter SMZ in the main exchange corresponding to the calling subscriber of the subsidiary exchange. The connecting of the corresponding meter takes place on the setting of selector DB30 in the subsidiary exchange by the switching device in the main exchange controlling this selector.

By the switching on of winding II of relay Y30 in the c-lead, which relay assists in sending out the control impulses, the existing connection is prevented from being released during this metering even when the calling subscriber replaces his receiver and thereby releases relay P30 which lies in the circuit of the speaking current. When the metering is completed and the calling subscriber replaces his receiver relays P30 and U3l deenergize. Since a locking circuit no longer exists for relay Y3i! in the c-lead it is disconnected by the opening of contact 3I9p30 so that it deenergizes. At contacts 3421 30 and 309u3| the operating circuit through magnet W3l and relay K30 in series is now closed again, so that now, in the same way as for the setting of selector DB30 on the calling subscriber, this is again controlled synchronously by the switching device in the main exchange. If the selector DB30 thus moves on to a subscribers line in which the subscriber has just taken up the receiver, seizing can at once take place again, since both the selector in the subsidiary exchange and the switching device in the main exchange are both in the same switching position, so that the meter in the main exchange corresponding to the calling subscriber is also connected up when the switches are brought to rest. If such a call does not occur, and selector DB30 and the controlling switching device in the main exchange accordingly reach position Ii, relay E30 energizes in the main exchange over: earth, battery, relay E30, wiper 11 III 33 in position II, contact 324x30, earth. Relay E3 establishes a locking circuit for itself over its contact 363630. The operating circuit passing over the bi lead is broken by contact 339230, and also battery is connected to lead b2 of the auxiliary connecting line, so that now magnet W32 of selector LW30 which stands in position I is influenced in series with relay K30 of the main exchange. The impulse circuit previously operating magnet D30 is correspondingly opened at contact 3l2e30 and is switched over to magnet D230 of the characterizing selector by the closing of contact 3l3e30. The auxiliary selector LW30 is accordingly switched on one step, and through the energizing of relay K30 in the same circuit magnet D130 is operated over contact 3|6k30, and likewise advances the characterizing selector one step. Relay Y30 is operated by the closing of contact 3l7dz'30, and by opening contact 342y30 breaks the operating circuit for the magnet W32 and relay K30. Contact 3l6k30 is accordingly opened, so that by the disconnection of magnet D230 and the associated opening of contact 3l'ldi30, relay Y30 is deenergized and the operating circuit for magnet W32 and relay K30 is again closed. This alternating play is repeated until the characterizing switching device has reached position H. When this occurs relay H30 is operated over wiper (ii I 30 and contact 361y30, and hence contact 3|4h30 is opened which now breaks the impulse circuit for magnet D230 and connects relay Y30 directly in this impulse circuit. Relay X30 deenergizes on the opening of contact 3'l2h30. The auxiliary selector LW30 is moved on further by means of impulses from the main exchange, but there the characterizing switching device does not move with it. The switching device LW30 continues to be advanced until it reaches position H. In this position earth is connected to the lead a2 over wiper d2 of the switching device LW30. Thus relay U32 is energized in the following circuit: earth, wiper a2 of the switching device LW30 in position I 1, winding I of relay U32, lead a2 of the connecting line, contact 344h30, resistance W219, battery, earth. By the opening of contact 302u32 the switching magnet W32 is disconnected and also the circuit of relay K30 is broken. The current is cut off from relay Y30 by the opening of contact 3|6Ic30 so that this relay opens contact 36ly30 and deenergizes relay H30. Contact 3481130 is opened and the energizing circuit of relay U32 described above is broken down. Contact 302u32 again closes the operating circuit for magnet W32 and relay K30, so that selector LW30 in the subsidiary exchange advances one step and likewise the magnet Di30 energized over contact 3|6k30 advances the characterizing switching device in the main exchange by one step. Accordingly both switching devices accomplish the last step into the normal position together. In the position 0 of wiper dz I 30 relay E30 remains energized over contacts 354h30 and 355030 until, since relay Y30 is energized over contact 3! 107,230 through the last switching step, relay H30is again energized over: earth, wiper di I 30 in position 0, contacts 365e30, 368x30, 30ly30, relay H30, battery, earth. By the opening of contact 304h30 the locking circuit for relay E30 is broken and this relay therefore deenergizes. Relay H30 holds up, after the opening of contact 305e30 over contact 3'l1h30. After contact 3!!di30 has opened relay Y30 again deenergizes. By the closing of contact 339.230 relay K30 is furthermore again connected to the B! lead of the connecting line and also preparation is made for switching in the magnet D30 of the switching device in the main exchange in the impulse circuit already described, over contact 3l2e30. Thereupon only magnet W3! is operated in series with relay K30. The latter causes relay Y30 to energize over contact M57030, so that this opens the energizing circuit of magnet W3! by opening contact 342y30. By the alternate play of these relays the switching magnet is influenced until the selector DB30 reaches position H. In this position the following circuit is set up: earth, wiper a! of selector DB30 in position !'i, winding I of relay U3l, lead a! of the connecting line, contacts 350030, 348an30, 345x30, 344h30, resistance Wil9, battery, earth. Relay U3! energizes and by opening contact 30003! disconnects the magnet W3!. Relays K30 and Y30 then also release so that now relay H30 is deenergized by the opening of contact 30ly30. Through the closing of contact 3!4h30 the switching magnet D30 in the main exchange is connected up while the energizing circuit just described for relay U3! is broken down at contact 344h30. The operating circuit for magnet W3! and relay K30 is accordingly closed again at contact 303u3l. The selector DB30 is thus advanced one step and moved into the normal position. At the same time magnet D30 isalso infiuenced by the closing of contact 3|0h30 so that the switching device in the main exchange similarly makes one switching step which takes it into the normal position. Since the wiper (1 IV 30 of this switching device has now left contact segments further advancement of the switching devices is not possible. All the devices both in the subsidiary and also in the main exchange are now again in the normal position.

Incoming trctfiic If a subscriber of the subsidiary exchange, for example A2 is called from the main exchange a final selector, which is not shown, is set by the corresponding numerical selection. If the connecting line leading to the subsidiary exchange is already seized the wiper d I 30 is not in the normal position, so that the final selector cannot test over the c-lead (02) corresponding to the desired subscriber. The wiper d I 30 remains away from the normal position as long as any of the switching devices of the connecting line either in the main exchange or in the subsidiary exchange are displaced from the normal position. Seizing the connecting line over a final selector is only possible when all these switching devices have reached the normal position. In the present case the final selector tests over the lead 02 corresponding to the subscriber A2. The circuit passes over resistance Wi20, contact 358030, relay A'rt30, wiper d I 30 in position 0, contact 3000 1130, resistance Wi22, battery, earth.

Relay An30 energizes in this circuit and locks up independently of wiper d I 30 over contact 35900130. At contact 34801130 battery is disconnected from the a! lead of the connecting line, so that no seizure of the connecting line can take place from the subsidiary exchange. t contact 336M230 battery is connected to lead 0! of the connecting line through relay K30. The following circuit is thus set up: earth, magnet W3!, contact 309u3l, lead b! of the connecting line, contacts 335030, 335an30, 339030, 342y30, relay K30, battery, earth. By the alternate play between magnet W3! and the magnet D30 in the main exchange operated by relays K30 or Y30 (as described in the case of outgoing traffic), the 1 selector DB30 in the subsdiary exchange is now advanced synchronously with the switching device in the main exchange operated by magnet D30. This advancement is continued until the wiper d1 30 has reached the lead 02 seized by the final selector. At this moment the selector DB3!) has also reached the second contact, to which subscriber A2 is connected. When this occurs relay C30 tests over contact 30!am30 and by opening contact 335030 prevents both the switching devices mentioned from being further advanced. At contacts 334030 and 349030 the speaking leads of the connecting line are switched over on the speaking leads of the final selectors. Relay A1130 now holds up over contact 351030. Ringing current can now be sent from the final selector, which is not shown, to the desired subscriber A2 of the subsidiary exchange in the known way. When the desired subscriber replies V the ringing current is disconnected in the final selector in any manner with which we are not now concerned. Relay U31 is operated over the subscriber's loop by the feeding current connected in the final selector, so that the I)! lead of the connecting line is switched through at contact 308u3l, and magnet W3! is disconnected at contact 309u3 The subscriber A2 is now connected to the final selector of the main exchange just as a normal subscriber having an individual line.

When the conversation has finished the 02 lead is disconnected in the final selector, relay C30 being thus deenergized. Contacts 334030 and 349030 open and break the circuit for the feeding current, so that relay U3! deenergizes. One effect of this is that the operating circuit for magnet W3! and relay K30 is closed through the closing of contact 309u3l. Through the alternate play of the corresponding relays the selector DB30 in the subsidiary exchange is advanced synchronously with the switching device in the main exchange. Thus, in the same way as was explained in the case of outgoing traflic, the selector in the subsidiary station is first advanced synchronously with the switching device in the main exchange until position I! is reached. Then it is moved on as far as position I! alone by means of impulses from the main station, whereupon it completes the final step into the normal position together with the switching device of the main exchange. During the release motion of the switching devices seizing cannot take place again until the two switching devices have returned to the normal position, since, in the case of an incoming call, relay X30 which takes up the initiation of a call is otherwise not energized.

Internal calls Seizing of the connecting line leading to the main exchange by the calling subscriber attached to the subsidiary exchange takes place in the same way as has already been described in the case of outgoing traffic. While in the case of outgoing traflic (exchange calls) the subscriber had to dial the characterizing digit 1, in the case of internal calls he must now dial the number which the desired subscriber has for internal calls, immediately. Since the digit 1 is employed for outgoing traffic, the internal numbers of the subscribers are limited to the numbers 2 to 10. Thus in this case nine subscribers can be attached to the subsidiary exchange.

As described above, relays J30 and V30 are energized during the dialling, while relay P30 is intermittently deen'ergized by the impulses, so that if for example the calling subscriber A2 desires a connection to subscriber A3 and accordingly dials the digit 3, magnet W32 received three impulses over the lead- 222 and contacts 374130 and 3751230 (impulse contact). The auxiliary selector LW30 is thus set on the third contact. The characterizing switching device is advanced synchronously by its magnet D230 to the third contact. After the dialling relay V30 is deenergized and relay Z30 is influenced over: earth, battery, relay Z30, contact 3051230, wiper di I 30 in position 3, earth. Since the impulse contact 3541030 in the main exchange loop is shunted during the dialling by contact 355730, the connecting devices of the main exchange are not set. By the opening of contact 353230 the p're-selecting device in the main exchange is now no longer seized. Since relay J30 remains energized over: earth, contacts 320y30, 322130, 32!p3!, wiper 112' III 30, relay J30, battery, earth, relay R30 is operated over: earth, battery, relay R30, contacts 369230, 370230, 3 second switch. Subscriber A3 is called by ringing current transmitted from the main exchange: ringing current source, contacts 330130, 332230, 3332130, lead a of the connecting line, winding I of relay U32, wiper a of the auxiliary selector LW30 in'position 3, subscriber A3, wiper b ofthe auxiliary selector LW30 in position 3, winding II of relay U32, contact 30311.32, earth. Since, relay R30 is influenced over a 3 second switch, ringing current is transmitted to the desired subscriber evcry 3 seconds. The calling subscriber receives part of this ringing current as a free signal over contact 3l0r30.

If the desired subscriber replies within a pause in the ringing i. e. at a moment when relay R30 is deenergized the following circuit is set up:

" earth, contact 30311.32, winding II of'relay U32,

wiper b2 of the auxiliary selector LW30 in position 3, subscriber A3, wiper a2 of the auxiliary selector LW30 in position 3, winding I of relay U32, lead a of the connecting line, contacts 333p30, 332230, 33!?30, winding I of relay P3l, battery, earth. In this circuit relays P3! and U32 energize. Since contact 3031032 is opened on the energizing of relay U32, the earth necessary for holding relays U32 and P3! energized is connected through contact 3| M73! and winding II of relay P3l, after the lead D2 of the connecting line has been switched through. Meanwhile relay J30 is deenergized by the opening of contact 32lp3! and relay R30 is deenergized by the opening of contact 369230, so that further transmission of ringing current is prevented. The feeding current for both subscribers is supplied from the main exchange. For subscriber A2 the circuit runs from the battery connected to lead a! and relay P30, to the earth connected through the choke coil D3! to lead bl, while for subscriber A3 current is fed from the battery connected through winding I of relay P3! to lead a2 of the connecting line, to the earth connected through winding II of relay P3! to lead 122.

Metering of internal calls takes place by the meter SM2 of the calling subscriber A2, connected through the switching device of the main exchange (wiper 11 II 30), being influenced over contacts 362230, 323y'30, 3201/30, and earth.

On the termination of the conversation, when the calling subscriber replaces his receiver relays P30 and U3! deenergize. Contact 3l9p30 opens and relay Y30 is thus deenergized, while by the opening of contact 3332730 relay P3! is deenergized. By the closing of contact 3421 30 battery is connected to the b! lead of the connecting line over relay K30, so that the magnet W3! of selector DB30 in the subsidiary exchange is energized. By the alternate play which has already been described above, the selector of the subsidiary exchange is advanced synchronously with the switching devices of the main exchange so that both switching devices are stepped round as far as position H. In position H relay E30 again energizes and causes the auxiliary selector LW30 in the subsidiary exchange to be advanced in the manner already described, under the influence of the corresponding magnet E32. The characterizing switching device D130 is switched on together with this selector. When these two switching devices reach the normal position by the switching operations described above, the selector DB30 of the subsidiary exchange is moved on automatically under the control of relays K30 and Y3!) in the main exchange until it reaches position II. It then completes the final switching step into the normal position together with the switching device in the main exchange.

This short description of the release motion should suifice, since a detailed description has already been given of the release in the case of an outgoing call.

If the called subscriber of an internal call does not reply, relay P30 releases when the calling subscriber replaces his receiver, while relay J30 is only released after the release of relay Y30. Accordingly the earth is disconnected from the metering circuit-by contact 3201/30 before contact 323130 closes so that in this case metering does not take place.

Special circuits If selector DB30 in the subsidiary exchange is displaced from the normal position by hand, earth is connected over contact 30! 103! to lead a2 over wiper a2 of the auxiliary selector LW30, so that relay X30 is energized in the main exchange and locks up over contact 373230. Battery is connected to the b! lead over contact 331.130 and thus the magnet W3! in the subsidiary exchange is influenced in series with relay K30 in the main exchange. The selector DB30 is now held until magnet D30 in the main exchange has been switched on through the closing of contact 3 I 6k30 whereupon both switching devices are advanced synchronously as in the case of a subscribers call, until they reach position H. In this position relay E30 energizes, as in the case above, and causes the auxiliary selector LW30 in the subsidiary exchange and the characterizing selector (rotary magnet Di) to advance synchronously to position I I, whereupon the auxiliary selector continues to advance alone into position [1 in precisely the same way as in the case of the release of an outgoing call, the last stepinto the normal position being executed together with the characterizing switching device. After this selector DB is advanced into position l1 and then finally into the normal position the last step being made together with the switching device of the main exchange. If the magnet W32 of the auxiliary selector is displaced from the normal position by hand contact 3051.032 (l-l1) connects earth over wiper al of the selector DB30 to the al lead of the connecting line, so that relay X30 is again influenced. In a manner corresponding to that above, selector DB30 and the switching device in the main exchange which is operated by magnet D30, are again advanced, whereupon after reaching position H, the magnet W32 of auxiliary selector LW30 is influenced synchronously with the characterizing switching device D230. The release motion thus takes the same course as is described above. If both selectors in the subsidiary exchange are displaced from the normal position simultaneously, then since contacts 0 and l are connected together in the auxiliary selector, earth is connected to the a2 lead of the connecting line over contract 30lw3l, so that again relay X30 is operated and the release motion described above takes place.

If the switching device in the main exchange which is operated by magnet D30 is displaced from the normal position by hand, battery is connected to lead b l over wiper d IV 30, and hence the selector DB30 in the subsidiary exchange and the switching device in the main exchange are advanced by the known interaction. All other operations take place as above. In contrast to the movements described above, the connecting line cannot be seized during this return motion, because relay X30, which prepares a circuit for the testing relay P30, is not energized. If the characterizing switching device which is operated by magnet D 30 is displaced by hand from the normal position, relay E30 energizes over wiper dz IV 30, and through contact 338e30 completes a circuit for magnet W32 in the subsidiary exchange and relay K30 in the main exchange, so that now the characterizing switching device in the main exchange and the auxiliary selector LW30 in the subsidiary exchange are advanced synchronously by the interaction as above. If, for example, at this moment seizing takes place on the part of the final selector in the main exchange, relays A1230 and C30 can be energized but the selector DB30 in the subsidiary exchange can only be set when the characterizing selector D230 is in the normal position, so that relay Z30 releases and by closing contact 339030 connects battery to the bi lead of the connecting line. Each seizure is indicated by the lighting up of the seizing lamp L. Seizing can also be recorded. If seizing in the incoming and outgoing directions is to be recorded separately the contacts 3127130 and 37 lan30 can be led separately to a recording device.

Having described the invention, what is considered to be new and is desired to be protected by Letters Patent will be set forth in the following claims:

What is claimed is:

1. In a telephone system, a main and a subsidiary exchange connected together, selector switches in said exchanges operated together to establish telephone connections between said exchanges, means for operating the switches in both exchanges in case any of them are not; operating together so as to restore them to their normal position, and means for preventing the establishment of a telephone connection While said switches are being restored.

2. In a telephone system, a main and a subsidiary exchange connected together, selector switches in both of said exchanges operated in synchronism to establish telephone connections from the subsidiary exchange, means responsive to a condition in which said switches are not operated in synchronism for operating them to their normal positions, and means for preventing the establishment of telephone connections from said subsidiary exchange during the time said switches are operating to their normal positions.

3. In an automatic telephone system, a main and a subsidiary exchange connected together, selector switches at both of said exchanges, the selector at the main exchange controlling the subsidiary exchange selectors and operating in synchronism therewith to establish an outgoing call from the subsidiary exchange, means operable in case said switches become out of step for operating them to their normal positions, and relay means operated when the selectors become out of step for preventing the establishment of an outgoing call from the subsidiary exchange over said selectors during the time said selectors are being restored to their normal positions.

4. In an automatic telephone system, a main and a subsidiary exchange connected together, selector switches at both of said exchanges, the main exchange selectors controlling the subsidiary selectors and operating in step therewith to establish an outgoing call from the subsidiary exchange, a testing relay in said main exchange for testing for the presence of a call from said subsidiary exchange, means operated in case said selector switches become out of step for operating them back to their normal positions, and means for rendering said testing relay inoperative during the restoring operation of said selector switch to prevent the establishment of an outgoing call from the subsidiary exchange.

5. In an automatic telephone system, as claimed in claim 4, means for breaking a partially prepared telephone connection in case it takes place during the restoring operation of said selector switches, the breaking of the connection preventing the testing of calling lines by said testing relay during said restoring operation.

6. In an automatic telephone system, a main and a subsidiary exchange connected together, selector switches at both of said exchanges, the main exchange switches controlling the subsidiary exchange switches and operating them in step therewith to establish outgoing calls from the subsidiary exchange, means in case said main exchange selectors are displaced from their normal position and therefore out of step with the subsidiary selectors for operating all of said selector switches to their normal positions again, means in the normal operating condition of said selector switches for testing for the presence of an outgoing call from the subsidiary exchange and for preparing for the establishment of the call, and means for breaking said call and preventing the testing for the presence. of the same at a time when said selector switches are displaced out of step and are being restored to their normal positions.

EDUARD WOCHINGER. 

